// download.js v3.0, by dandavis; 2008-2014. [CCBY2] see http://danml.com/download.html for tests/usage
// v1 landed a FF+Chrome compat way of downloading strings to local un-named files, upgraded to use a hidden frame and optional mime
// v2 added named files via a[download], msSaveBlob, IE (10+) support, and window.URL support for larger+faster saves than dataURLs
// v3 added dataURL and Blob Input, bind-toggle arity, and legacy dataURL fallback was improved with force-download mime and base64 support

// data can be a string, Blob, File, or dataURL

function download(data, strFileName, strMimeType) {
  var self = window // this script is only for browsers anyway...
  var defaultMime = 'application/octet-stream' // this default mime also triggers iframe downloads
  var mimeType = strMimeType || defaultMime
  var payload = data
  // url = !strFileName && !strMimeType && payload,
  var url = payload
  var anchor = document.createElement('a')
  var toString = function(a) { return String(a) }
  var MyBlob = (self.Blob || self.MozBlob || self.WebKitBlob || toString)
  var fileName = strFileName || 'download'
  var blob
  var reader
  MyBlob = MyBlob.call ? MyBlob.bind(self) : Blob

  if (String(this) === 'true') { // reverse arguments, allowing download.bind(true, "text/xml", "export.xml") to act as a callback
    payload = [payload, mimeType]
    mimeType = payload[0]
    payload = payload[1]
  }

  if (url && url.length < 2048) { // if no filename and no mime, assume a url was passed as the only argument
    fileName = url.split('/').pop().split('?')[0]
    anchor.href = url // assign href prop to temp anchor
    if (anchor.href.indexOf(url) !== -1) { // if the browser determines that it's a potentially valid url path:
      var ajax = new XMLHttpRequest()
      ajax.open('GET', url, true)
      ajax.payloadType = 'blob'
      ajax.onload = function(e) {
        download(e.target.payload, fileName, defaultMime)
      }
      setTimeout(function() { ajax.send() }, 0) // allows setting custom ajax headers using the return:
      return ajax
    } // end if valid url?
  } // end if url?

  // go ahead and download dataURLs right away
  if (/^data\:[\w+\-]+\/[\w+\-]+[,;]/.test(payload)) {
    if (payload.length > (1024 * 1024 * 1.999) && MyBlob !== toString) {
      payload = dataUrlToBlob(payload)
      mimeType = payload.type || defaultMime
    } else {
      return navigator.msSaveBlob // IE10 can't do a[download], only Blobs:
        ? navigator.msSaveBlob(dataUrlToBlob(payload), fileName)
        : saver(payload) // everyone else can save dataURLs un-processed
    }
  }// end if dataURL passed?

  blob = payload instanceof MyBlob
    ? payload
    : new MyBlob([payload], { type: mimeType })

  function dataUrlToBlob(strUrl) {
    var parts = strUrl.split(/[:;,]/)
    var type = parts[1]
    var decoder = parts[2] === 'base64' ? atob : decodeURIComponent
    var binData = decoder(parts.pop())
    var mx = binData.length
    var i = 0
    var uiArr = new Uint8Array(mx)

    for (i; i < mx; ++i) uiArr[i] = binData.charCodeAt(i)

    return new MyBlob([uiArr], { type: type })
  }

  function saver(url, winMode) {
    if ('download' in anchor) { // html5 A[download]
      anchor.href = url
      anchor.setAttribute('download', fileName)
      anchor.className = 'download-js-link'
      anchor.innerHTML = 'downloading...'
      anchor.style.display = 'none'
      document.body.appendChild(anchor)
      setTimeout(function() {
        anchor.click()
        document.body.removeChild(anchor)
        if (winMode === true) { setTimeout(function() { self.URL.revokeObjectURL(anchor.href) }, 250) }
      }, 66)
      return true
    }

    // handle non-a[download] safari as best we can:
    if (/(Version)\/(\d+)\.(\d+)(?:\.(\d+))?.*Safari\//.test(navigator.userAgent)) {
      url = url.replace(/^data:([\w\/\-\+]+)/, defaultMime)
      if (!window.open(url)) { // popup blocked, offer direct download:
        if (confirm('Displaying New Document\n\nUse Save As... to download, then click back to return to this page.')) { location.href = url }
      }
      return true
    }

    // do iframe dataURL download (old ch+FF):
    var f = document.createElement('iframe')
    document.body.appendChild(f)

    if (!winMode) { // force a mime that will download:
      url = 'data:' + url.replace(/^data:([\w\/\-\+]+)/, defaultMime)
    }
    f.src = url
    setTimeout(function() { document.body.removeChild(f) }, 333)
  }// end saver

  if (navigator.msSaveBlob) { // IE10+ : (has Blob, but not a[download] or URL)
    return navigator.msSaveBlob(blob, fileName)
  }

  if (self.URL) { // simple fast and modern way using Blob and URL:
    saver(self.URL.createObjectURL(blob), true)
  } else {
    // handle non-Blob()+non-URL browsers:
    if (typeof blob === 'string' || blob.constructor === toString) {
      try {
        return saver('data:' + mimeType + ';base64,' + self.btoa(blob))
      } catch (y) {
        return saver('data:' + mimeType + ',' + encodeURIComponent(blob))
      }
    }

    // Blob but not URL support:
    reader = new FileReader()
    reader.onload = function(e) {
      saver(this.result)
    }
    reader.readAsDataURL(blob)
  }
  return true
} /* end download() */

export default download
